Soft plastic squeaky dog toys.
When Molly was a wee pup (a very wee pup, she's 15lbs full grown) her first toys were cheap little soft plastic squeakies purchased at one of our Big Two supermarket chains, mostly in the form of sea creatures. They were small enough and soft enough that her little mouth didn't get hurt chewing them, they squeaked very loudly (annoying, but it got her attention when she wandered off in the paddock) and were tough enough to last a good few tug-o-war matches before they punctured. She loved them then, and at 4 years old she still loves them now, over every other toy she has. And she (and Suzi) are not deprived pups by any means.
Now they no longer stock them. There are heaps of other plastic squeaky toys available, but the plastic is much harder, and neither of them will touch them. Or the toys are too big to get their little mouths around. Or they have spikes on them that both dogs don't like.
We still have a heap of the favourite squeakies in the toy basket, but they've all lost their squeak now, and that's a major part of the fun for Molly, at least. She just has to hear the squeak and she's off doing a little dance to start the game. Luckily she'll play with them till they're in shreds, but still, it would be nice to replace the ones we have when they're totally used up.
I've looked everywhere for them, no dice.